With the rapid development of portable electronic devices, wire control apparatuses have been developed that can enable users to conveniently operate the electronic devices from an external device, such as a wire control apparatus. For example, users can implement control of music playing, answer a call, control volume, and so on using said external device.
Some buttons are generally provided on the wire control apparatuses to implement different control functions, and the electronic devices identify that a certain button is pressed through the detection of a button-press signal. However, in practical applications, the button-press signal generally contains noise interference signals. In order to accurately perform button-press detection and avoid failure and omission of button-press detection due to the noise interference signals, in normal cases, a customized button-press signal transmitting chip are required on the wire control apparatus with a matching button-press signal receiving chip on the electronic device.
As shown in FIG. 1, a mobile device, such as the iPod® from Apple Inc., can be provided with a wire control handset. The wire control handset is includes a dedicated digital signal transmitting chip IC1 configured to identify a pressed button and generate a corresponding digital signal. Similarly, the mobile device can include a dedicated digital signal receiving chip IC2 configured to receive the digital signal and transmit the digital signal to an audio codec 32 as a control signal. The audio codec 32 can control a left sound channel signal (L_SPKR) and a right sound channel signal (R_SPKR) transmitted to the wire control handset according to a control signal. Failure or omission of button-press detection due to noise interference signals can be avoided using the dedicated digital signal transmitting and receiving chips IC1, IC2, but the dedicated chips need to be arranged on both the wire control apparatus and the electronic device, which greatly increases the manufacturing cost.
In addition, failure or omission of button-press detection due to noise interference signals can be avoided by filtering the button-press signal using software, but the filtering requires complex software codes, which increases the processing capacity of codes of an operating system of the electronic device and is not beneficial to the product design.
In certain applications, passgates can be employed to pass a signal between two nodes of an electronic device. For example, a passgate can be used to pass a signal from an electronic device, such as a portable electronic device, to an accessory device connected to the electronic device. Passgates can be used to pass analog signals, such as analog audio signals, between devices. Design criteria for passgate control circuits can influence how well a passgate can pass certain analog signals without introducing distortion and how well a passgate can isolate the two nodes when the passgate is not enabled. Some analog passgates and corresponding passgate controls are made using high-voltage processes such that the passgate and control circuits can withstand reception of higher voltage signals. Such high-voltage devices and processes to make such devices can add costs to products using such devices.